Several recent studies have shown that sitting for long periods of time can harm our health, weakening muscles and decreasing overall physical fitness.

And now, a new analysis of several studies on long periods of sedentary behavior has concluded that sitting for more than three hours a day can actually take two years off your life.

And that's even if you exercise regularly and refrain from bad habits like smoking.

But there's more bad news.

They've also determined that watching TV for more than two hours a day cuts your life expectancy by another 1.4 years.

Details of the study

The researchers, Peter T. Katzmarzyk, a professor of population science at the Pennington Biomedical Research Center in Baton Rouge, La., and I-Min Lee of Brigham and Women's Hospital and Harvard Medical School, analyzed five studies of nearly 167,000 people over four to 14 years.

They used the National Health and Nutrition Examination Survey to get data on sitting habits between 2009 and 2010 and to obtain data on TV watching from 2005 to 2006 (the most recent data available).

They eliminated data on patients who had existing diseases since the ill were more likely to be sitting more than usual due to health reasons.

However, one drawback to the analysis was that it relied on self-reporting, and people tend to underestimate how much they sit.

How to beat the sedentary lifestyle

Combating the effects of sitting a lot isn't as easy as throwing in a workout here and there.

Dr. Katzmarzyk said that the detrimental effects of sitting affect even people who follow the guideline of getting 30 minutes of physical activity a day. He told The Wall Street Journal:

"We have people who can meet that guideline. However, if you're sedentary or sitting the other 20 hours a day, you're still going to be at risk for that."

A big problem is the type of lifestyle associated with a desk job, where people can sit for hours a day. For such workers, Dr. Katzmarzyk suggested trying to stand as often as possible: "Typically when you're on the telephone you can stand with speaker phone. Instead of emailing someone in the office, just get up and go talk to them."

Engaging in regular activity like that prevents your leg muscles from being completely inactive and your body from running into trouble managing blood glucose.

What the results mean is that we got everyone in the U.S. to sit less, our population life expectancy would be two years higher, so instead of living to 78.5, we would be expected to live to 80.5 years old, Dr. Katzmarzyk told Time. "That;s a really big deal".

Even more bad news for sitters

This is just the latest in a string of studies on the ill effects of sitting:

Two years ago, Australian researchers found that people who watched TV for more than four hours a day were 46% more likely to die than people who spent less than two hours a day watching TV. The first group also had an 80% higher risk of dying from cardiovascular disease.

Last year, a study found that people who spent 10 years in sedentary jobs had double the risk of colon cancer and a 44% higher risk of rectal cancer, compared with those who had never had sedentary jobs.

Last November, a study concluded that sitting too much leads to 92,000 cases of cancer a year.

This past March, a study of 265,000 people showed that people who sit for 11 or more hours a day were 40% more likely to die from any cause than people who sat less than four hours a day.

Correction: In the first version of this post, I stated that if the study subjects underreported their hours of sitting, the effect on life expectancy was likely to be worse. Readers correctly pointed out that I had made the wrong conclusion: the effect on life expectancy is likely to be smaller.